US7702377B2 - Magnetic resonance imaging - Google Patents
Magnetic resonance imaging Download PDFInfo
- Publication number
- US7702377B2 US7702377B2 US11/568,226 US56822605A US7702377B2 US 7702377 B2 US7702377 B2 US 7702377B2 US 56822605 A US56822605 A US 56822605A US 7702377 B2 US7702377 B2 US 7702377B2
- Authority
- US
- United States
- Prior art keywords
- magnetic resonance
- trigger
- resonance imaging
- events
- detected
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related, expires
Links
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
- G01R33/48—NMR imaging systems
- G01R33/54—Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console
- G01R33/56—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution
- G01R33/567—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution gated by physiological signals, i.e. synchronization of acquired MR data with periodical motion of an object of interest, e.g. monitoring or triggering system for cardiac or respiratory gating
- G01R33/5673—Gating or triggering based on a physiological signal other than an MR signal, e.g. ECG gating or motion monitoring using optical systems for monitoring the motion of a fiducial marker
Definitions
- the invention relates to a magnetic resonance imaging method in which magnetic resonance signals are acquired from a dynamically varying object and a magnetic resonance image is reconstructed from the magnetic resonance signals.
- Magnetic Resonance Imaging by M. T. Vlaardingerbroek and J. A. den Boer, (2 nd edition, Springer Verlag Berlin, 1999) such a magnetic resonance imaging method is known which is in particular directed to imaging the beating heart of the patient to be examined.
- the movement and changes in shape and size of the beating heart form the dynamic variations of the object.
- Magnetic Resonance Imaging by M. T. Vlaardingerbroek and J. A. den Boer, (2 nd edition, Springer Verlag Berlin, 1999) mentions that a way to cope with cardiac motion in magnetic resonance imaging is to trigger the acquisition of the magnetic resonance signals by the cardiac rhythm using an electrocardiogram (ECG).
- ECG electrocardiogram
- Profiles of magnetic resonance signals are acquired in the same heart phase where the heart has returned to the same position. At a predetermined delay after a detected R-peak only one profile is measured and the rest of the R-R interval can be used for the acquisition of data from other slices.
- An object of the invention is to provide an magnetic resonance imaging method achieving an improved image quality and efficiency of the signal acquisition in order to image dynamic variations of an object.
- the present invention is based on the insight that irregularities or changes in the dynamic variations can be prospectively taken into account.
- the dynamic variations often involve some degree of regularity, such as some periodicity.
- Taking previously detected trigger events in to account when setting the acquisition of the current segment of magnetic resonance signals achieves that the changes in the dynamic variations are appropriately taken into account in the acquisition of the current segment of magnetic resonance signals.
- slow drift of the periodicity of e.g. the heartbeat of the patient to be examined is accurately taken into account.
- errors that are due to incorrect or no accounting for changes in the dynamic variations are reduced or avoided.
- perturbations, e.g. motion artifacts in the reconstructed magnetic resonance image are avoided.
- the efficiency of the signal acquisition is improved because there is no need to discard magnetic resonance signals that were acquired incorrectly in relation to their detected trigger event.
- Magnetic resonance signals are acquired in the form of respective segments. Individual segments of magnetic resonance signals are acquired by scanning respective segments of k-space. In particular lines or groups of a small number of lines in k-space form such segments of k-space.
- the magnetic resonance image is reconstructed from the magnetic resonance signals from several segments of magnetic resonance signals. These respective magnetic resonance signals are acquired upon different trigger events.
- the next trigger event is predicted on the basis of a series of earlier trigger events.
- a typical trigger event in cardiac magnetic resonance imaging is the detection of an R-peak in the patient's ECG.
- the acquisition of the next segment of magnetic resonance signals is set.
- the setting of the acquisition may involve the instant and duration of the acquisition upon the current trigger event of the current segment of magnetic resonance signals, or the setting may involve that the acquisition foreseen upon the current trigger event is discarded and that the next acquisition is done at a later occurring trigger event. For example, when the diff
- the actual instant of the detected current trigger event is compared with the prediction of the current trigger event.
- the acquisition of the current segment of magnetic resonance signals is done in dependence of this comparison.
- the actual instant of the trigger event differs significantly, e.g. the difference between the actual instant and its prediction being larger than a pre-determined threshold value
- the acquisition of the current segment of magnetic resonance signals is discarded and carried out again upon a next trigger event.
- Such a significant difference between the actual and predicted instant of the current trigger event signals a substantial deviation of the regularity of the dynamic variations.
- the acquisition of the current segment of magnetic resonance signals is very likely to be affected by artifacts, such as motion artifacts. Discarding and re-acquisition of the current segment of magnetic resonance signals avoids these artifacts to proliferate into the reconstructed magnetic resonance image.
- a selection of trigger events of the detected series is made and the dependence of the acquisition of the current segment of magnetic resonance signals is made on the basis of the selected trigger events.
- This aspect of the invention is based on the insight that in many situations it is possible to distinguish trigger events that pertain to a regular dynamic behavior of the dynamics from trigger events that reflect irregularities of the dynamic behavior. Part of the detected trigger events, notably trigger events that reflect irregular dynamic behavior are not taken into account for the prediction of the next trigger event. In this way, erroneous trigger events, or trigger events that are due to irregularities which are not included in the selection do not adversely affect the prediction of the next trigger event. Hence, a more accurate prediction of this next trigger event is achieved.
- the selection of trigger events can be done on the basis of monitoring events. These monitoring events are other events than the trigger events. These monitoring events represent the dynamic behavior of a phenomenon that is different from the phenomenon on which the triggering events are based.
- the triggering is typically based on the ECG signal and the monitoring events concern a respiration state of the patient to be examined.
- the trigger events formed by R-peaks in the ECG can be selected on the basis of coincidence with either the occurrence of an expiration state or of an inspiration state of the patient's breathing.
- Another example of a monitor event that can be employed for the selection of trigger event is the motion of the patient. To detect the patient's respiration state, for example, motion of the patient's chest can be also used.
- the next trigger event is predicted on the basis of a statistical analysis of the instants of the previous trigger events.
- a statistical analysis enables to distinguish between trigger events that pertain to regular dynamic behavior from trigger events that reflect notably unpredictable irregularities.
- irregularities may be R-peaks that relate to additional systoles or early or late systoles.
- Very good results are achieved by employing a running average over the time intervals between previous trigger events.
- the prediction of the next trigger event can be made more accurate by taking the running average of only the selected trigger events, e.g. on the basis of the occurrence of monitoring such the previous trigger events coinciding with a definite respiration state.
- the statistical analysis is implemented as a recurring estimate of the interval between the occurrences of trigger events.
- This implementation involves a recurrence parameter which is easily adjustable and results in an exponentially decaying weight for less recent trigger events.
- the invention further relates to a magnetic resonance imaging system according to the invention as defined.
- a further version of the magnetic resonance imaging system of the invention is defined.
- the magnetic resonance imaging system of the invention is capable of performing the magnetic resonance imaging method of the invention and according performs a more accurate triggering of the acquisition of magnetic resonance signals.
- the invention further pertains to a computer program as defined.
- the computer program of the invention When loaded into the working memory of a processor of a magnetic resonance imaging system, the computer program of the invention enables the magnetic resonance imaging system to perform the magnetic resonance imaging method of the invention. That is to achieve a more accurate triggering of the acquisition of magnetic resonance signals.
- the computer program can be provided on a data carrier such as a CD-rom.
- the computer program can be downloaded from a remote site via a data network, such as the world-wide web; notably the computer program can be downloaded from a web-address of web page via the internet.
- FIG. 1 shows diagrammatically a magnetic resonance imaging system in which the invention is used
- FIG. 2 shows a graph representing the weighting function that are employed in the running average
- the FIG. 1 shows diagrammatically a magnetic resonance imaging system in which the invention is used.
- the magnetic resonance imaging system includes a set of main coils 10 whereby the steady, uniform magnetic field is generated.
- the main coils are constructed, for example in such a manner that they enclose a tunnel-shaped examination space.
- the patient to be examined is placed on a patient carrier which is slid into this tunnel-shaped examination space.
- the magnetic resonance imaging system also includes a number of gradient coils 11 , 12 whereby magnetic fields exhibiting spatial variations, notably in the form of temporary gradients in individual directions, are generated so as to be superposed on the uniform magnetic field.
- the gradient coils 11 , 12 are connected to a controllable power supply unit 21 .
- the magnetic resonance imaging system also includes transmission and receiving coils 13 , 16 for generating the RF excitation pulses and for picking up the magnetic resonance signals, respectively.
- the transmission coil 13 is preferably constructed as a body coil 13 whereby (a part of) the object to be examined can be enclosed.
- the body coil is usually arranged in the magnetic resonance imaging system in such a manner that the patient 30 to be examined is enclosed by the body coil 13 when he or she is arranged in the magnetic resonance imaging system.
- the body coil 13 acts as a transmission antenna for the transmission of the RF excitation pulses and RF refocusing pulses.
- the body coil 13 involves a spatially uniform intensity distribution of the transmitted RF pulses (RFS).
- the same coil or antenna is usually used alternately as the transmission coil and the receiving coil.
- the transmission and receiving coil is usually shaped as a coil, but other geometries where the transmission and receiving coil acts as a transmission and receiving antenna for RF electromagnetic signals are also feasible.
- the transmission and receiving coil 13 is connected to an electronic transmission and receiving circuit 15 .
- receiving and/or transmission coils 16 can be used as receiving and/or transmission coils. Such surface coils have a high sensitivity in a comparatively small volume.
- the receiving coils such as the surface coils, are connected to a demodulator 24 and the received magnetic resonance signals (MS) are demodulated by means of the demodulator 24 .
- the demodulated magnetic resonance signals (DMS) are applied to a reconstruction unit.
- the receiving coil is connected to a preamplifier 23 .
- the preamplifier 23 amplifies the RF resonance signal (MS) received by the receiving coil 16 and the amplified RF resonance signal is applied to a demodulator 24 .
- the demodulator 24 demodulates the amplified RF resonance signal.
- the demodulated resonance signal contains the actual information concerning the local spin densities in the part of the object to be imaged.
- the transmission and receiving circuit 15 is connected to a modulator 22 .
- the modulator 22 and the transmission and receiving circuit 15 activate the transmission coil 13 so as to transmit the RF excitation and refocusing pulses.
- the reconstruction unit derives one or more image signals from the demodulated magnetic resonance signals (DMS), which image signals represent the image information of the imaged part of the object to be examined.
- the reconstruction unit 25 in practice is constructed preferably as a digital image processing unit 25 which is programmed so as to derive from the demodulated magnetic resonance signals the image signals which represent the image information of the part of the object to be imaged.
- the signal on the output of the reconstruction is applied to the monitor 26 , so that the monitor can display the magnetic resonance image. It is alternatively possible to store the signal from the reconstruction unit 25 in a buffer unit 27 while awaiting further processing.
- the magnetic resonance imaging system is also provided with a control unit 20 , for example in the form of a computer which includes a (micro)processor.
- the control unit 20 controls the execution of the RF excitations and the application of the temporary gradient fields.
- the operation of the control unit 20 is in turn regulated by a trigger unit 40 that applies trigger signals to the control unit in order to activate on the basis of the occurrence of a trigger event the magnetic resonance imaging system to acquire segments of magnetic resonance signals from respective segments of k-space.
- An electrocardiography unit 42 notably operating on the basis of a vector electrocardiogram, acquires ECG signals from the patient's heart.
- An ECG device that operates on the basis of a vector electrocardiogram is suitable be employed as the electrocardiography unit and is known as such in magnetic resonance imaging from the international application WO99/04688.
- the ECG signals are applied to a statistical analyzer unit 41 which makes a statistical analysis of the received ECG signals to predict the occurrence of a next trigger event.
- the statistical analysis unit 41 predicts when the next R-peak is the patient's ECG will occur. Further, the statistical analysis unit calculates the instant and duration of the next segment of the magnetic resonance signal acquisition controlled by the control unit 20 .
- the statistical analysis unit for example takes account of variations in the patient's heart rate in accurately determining a time interval that accurately coincides diastolic phase in which the patient's heart is hardly moving. During that time interval the current segment of magnetic resonance signals is acquired and motion hardly affects this segment of magnetic resonance signals.
- the magnetic resonance imaging system of the invention is further provided with a monitor 43 which detects the monitoring events, notably in the form of the patient's respiratory state.
- the detected monitoring event is communicated to the statistical analysis unit 41 which takes account of the detected monitoring event in predicting the occurrence of the next trigger event.
- the monitoring unit may be arranged to measure the patient's respiratory state, that is to determine inspiration and expiration.
- the statistical analysis unit is arranged to account for a slightly longer, e.g. by 5-10% interval between R-peaks in the patient's ECG during expiration.
- the interval between R-peaks of an individual may vary by 5-10% between inspiration and expiration.
- the weighting function w i is a non-decreasing function or an increasing function as a function of time. Examples are shown in the graphs in FIG. 2 .
- the value of the weighting factor is plotted as a function of successive trigger events, or equivalently of time. The current instant is indicated as point n.
- Graph (a) shows a simple weighting factor that has a constant value in the interval (n-N, n).
- Graph (b) shows a weighting factor that linearly increases in the interval (n-N, n).
- Graph c shows a weighting factor that linearly increases in an interval (n-N,j) and remains constant in an interval (j,n).
- the weighted running average provides a more accurate prediction of the patient's current heart rate.
- the function f may also implement a respiratory acceptance gating in that
- RR n ( N ) aRR n +( a ⁇ 1) RR n ⁇ 1 ( N ) which leads to a temporal weighting function that exponentially decays into the past.
- Kalman filtering Another alternative is to employ Kalman filtering to predict the next R-R interval.
- Kalman filters are known as such from ‘A new approach to linear filtering and prediction problems’ in Trans AMSE, J. Basic Engineering 82 series D(1060)35-45.
- the computer program according to the invention is loaded, for example, into the control unit 20 and the reconstruction unit 25 .
Landscapes
- Health & Medical Sciences (AREA)
- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Physiology (AREA)
- Biophysics (AREA)
- Life Sciences & Earth Sciences (AREA)
- Power Engineering (AREA)
- Pulmonology (AREA)
- General Health & Medical Sciences (AREA)
- Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
- Radiology & Medical Imaging (AREA)
- Signal Processing (AREA)
- Cardiology (AREA)
- High Energy & Nuclear Physics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Magnetic Resonance Imaging Apparatus (AREA)
Abstract
Description
-
- a series of trigger events is detected
- segments of magnetic resonance signals are acquired from respective segments of k-space upon a respective detected trigger events and
- the acquisition of an individual segment of magnetic resonance signals upon its detected trigger event is dependent on previously detected trigger events.
then the next R-R interval is predicted to equal the current weighted running average:
RR n+1 = RR n(N)
w i ′=w i f(G i)g(RR i)
where wi is one of the non-decreasing functions shown in
A further refinement is achieved by combining the respiratory acceptance gating with the exclusion of arrhythmic R-R intervals.
RR n(N)=aRR n+(a−1) RR n−1(N)
which leads to a temporal weighting function that exponentially decays into the past.
Claims (18)
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP04101750.0 | 2004-04-27 | ||
EP04101750 | 2004-04-27 | ||
EP04101750 | 2004-04-27 | ||
PCT/IB2005/051300 WO2005103750A1 (en) | 2004-04-27 | 2005-04-21 | Magnetic resonance imaging |
Publications (2)
Publication Number | Publication Date |
---|---|
US20080154121A1 US20080154121A1 (en) | 2008-06-26 |
US7702377B2 true US7702377B2 (en) | 2010-04-20 |
Family
ID=34964520
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US11/568,226 Expired - Fee Related US7702377B2 (en) | 2004-04-27 | 2005-04-21 | Magnetic resonance imaging |
Country Status (5)
Country | Link |
---|---|
US (1) | US7702377B2 (en) |
EP (1) | EP1743189A1 (en) |
JP (1) | JP2007534417A (en) |
CN (1) | CN1950715A (en) |
WO (1) | WO2005103750A1 (en) |
Families Citing this family (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE102013207458A1 (en) * | 2013-04-24 | 2014-10-30 | Siemens Aktiengesellschaft | Method for correcting an ECG signal during magnetic resonance imaging and ECG triggering device |
EP3077837A1 (en) * | 2013-12-02 | 2016-10-12 | Koninklijke Philips N.V. | Real-time adaptive physiology synchronization and gating for steady state mr sequences |
CN104688219A (en) * | 2013-12-04 | 2015-06-10 | 乐普(北京)医疗器械股份有限公司 | Electrocardiosignal prediction method and electrocardiosignal prediction system |
US11428768B2 (en) * | 2017-04-05 | 2022-08-30 | The General Hospital Corporation | Chemical exchange saturation transfer magnetic resonance imaging with gating synchronized acquisition |
DE102017206182A1 (en) | 2017-04-11 | 2018-10-11 | Siemens Healthcare Gmbh | Method for recording a magnetic resonance data set, data carrier and magnetic resonance system |
CN113749637A (en) * | 2020-06-04 | 2021-12-07 | 西门子(深圳)磁共振有限公司 | Magnetic resonance data acquisition triggering method and device and readable storage medium |
Citations (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4710717A (en) * | 1986-12-29 | 1987-12-01 | General Electric Company | Method for fast scan cine NMR imaging |
EP0256584A1 (en) | 1986-08-14 | 1988-02-24 | North American Philips Corporation | Method and apparatus for MR imaging |
EP0412695A2 (en) | 1989-08-11 | 1991-02-13 | Picker International, Inc. | Magnetic resonance imaging |
WO1999004688A1 (en) | 1997-07-23 | 1999-02-04 | Koninklijke Philips Electronics N.V. | Ecg triggered mr imaging method and apparatus |
US6070097A (en) * | 1998-12-30 | 2000-05-30 | General Electric Company | Method for generating a gating signal for cardiac MRI |
US6078175A (en) * | 1998-10-26 | 2000-06-20 | General Electric Company | Acquistion of segmented cardiac gated MRI perfusion images |
US6611701B2 (en) * | 2000-12-30 | 2003-08-26 | Ge Medical Systems Global Technology Company, Llc | Method and apparatus for fast breath-held 3D MR data acquisition using variable sampling |
US20040030234A1 (en) | 2000-08-25 | 2004-02-12 | Zamir Hayek | Mri method |
-
2005
- 2005-04-21 US US11/568,226 patent/US7702377B2/en not_active Expired - Fee Related
- 2005-04-21 JP JP2007510189A patent/JP2007534417A/en not_active Withdrawn
- 2005-04-21 EP EP05718777A patent/EP1743189A1/en not_active Withdrawn
- 2005-04-21 WO PCT/IB2005/051300 patent/WO2005103750A1/en not_active Application Discontinuation
- 2005-04-21 CN CNA2005800136072A patent/CN1950715A/en active Pending
Patent Citations (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0256584A1 (en) | 1986-08-14 | 1988-02-24 | North American Philips Corporation | Method and apparatus for MR imaging |
US4710717A (en) * | 1986-12-29 | 1987-12-01 | General Electric Company | Method for fast scan cine NMR imaging |
EP0412695A2 (en) | 1989-08-11 | 1991-02-13 | Picker International, Inc. | Magnetic resonance imaging |
US5000182A (en) * | 1989-08-11 | 1991-03-19 | Picker International, Inc. | Cardiac synchronization magnetic resonance imaging |
WO1999004688A1 (en) | 1997-07-23 | 1999-02-04 | Koninklijke Philips Electronics N.V. | Ecg triggered mr imaging method and apparatus |
US6078175A (en) * | 1998-10-26 | 2000-06-20 | General Electric Company | Acquistion of segmented cardiac gated MRI perfusion images |
US6070097A (en) * | 1998-12-30 | 2000-05-30 | General Electric Company | Method for generating a gating signal for cardiac MRI |
US20040030234A1 (en) | 2000-08-25 | 2004-02-12 | Zamir Hayek | Mri method |
US6611701B2 (en) * | 2000-12-30 | 2003-08-26 | Ge Medical Systems Global Technology Company, Llc | Method and apparatus for fast breath-held 3D MR data acquisition using variable sampling |
Non-Patent Citations (2)
Title |
---|
Kalman, R.E.; A New Approach to Linear Filtering and Prediction Problems; 1960; Journal of Basic Engineering; pp. 35-45. |
Vlaardingerbroek, M.T., et al.; Magnetic Resonance Imaging, 1999; 2nd Ed.; Springer Verlag Berlin; pp. 354-360. |
Also Published As
Publication number | Publication date |
---|---|
EP1743189A1 (en) | 2007-01-17 |
US20080154121A1 (en) | 2008-06-26 |
CN1950715A (en) | 2007-04-18 |
JP2007534417A (en) | 2007-11-29 |
WO2005103750A1 (en) | 2005-11-03 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
EP2509505B1 (en) | Method and apparatus for using time of flight information to detect and correct for motion in imaging scans | |
KR101939445B1 (en) | Method for ascertaining an item of movement information describing a movement in an at least partially moved examination region, and magnetic resonance device | |
US7561909B1 (en) | MRI navigator methods and systems | |
US5000182A (en) | Cardiac synchronization magnetic resonance imaging | |
US7702377B2 (en) | Magnetic resonance imaging | |
US9202272B2 (en) | Method and apparatus for image enhancement in magnetic resonance imaging using motion corrupted data | |
US10302732B2 (en) | Real-time adaptive physiology synchronization and gating for steady state MR sequences | |
JP6388877B2 (en) | System and method for improved cardiac imaging of subjects with adverse cardiac conditions | |
CN103376434B (en) | By the method for the measurement data set of the check object of mr techniques collection breathing | |
US11471065B2 (en) | Medical image diagnosis apparatus | |
US20190274569A1 (en) | Method for determining diastasis timing using an mri septal scout | |
JP3992973B2 (en) | Acquisition of freely breathing MR images with high temporal resolution | |
US20150157277A1 (en) | Magnetic resonance imaging apparatus and magnetic resonance imaging method | |
US8909321B2 (en) | Diagnostic imaging apparatus, magnetic resonance imaging apparatus, and X-ray CT apparatus | |
JP4934525B2 (en) | Nuclear magnetic resonance apparatus | |
EP1437602B1 (en) | Inspection apparatus using nuclear magnetic resonance | |
US7548777B2 (en) | Computerized method for predicting the diastolic rest period in a cardiac cycle | |
US7480526B2 (en) | Method for mapping an examination volume in an MR spectrometer | |
US11766188B2 (en) | Magnetic resonance imaging device |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: KONINKLIJKE PHILIPS ELECTRONICS N.V., NETHERLANDS Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:KOUWENHOVEN, MARC;REEL/FRAME:018425/0769 Effective date: 20051117 Owner name: KONINKLIJKE PHILIPS ELECTRONICS N.V.,NETHERLANDS Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:KOUWENHOVEN, MARC;REEL/FRAME:018425/0769 Effective date: 20051117 |
|
REMI | Maintenance fee reminder mailed | ||
LAPS | Lapse for failure to pay maintenance fees | ||
STCH | Information on status: patent discontinuation |
Free format text: PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362 |
|
FP | Lapsed due to failure to pay maintenance fee |
Effective date: 20140420 |